.box {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 900px;
  border: 1px solid black;
}
.box ul {
  width: 100%;
  overflow: hidden;
}
.box ul li {
  float: left;
  width: 33.333%;
}
.box ul li img {
  width: 100%;
  display: block;
}
.box .cover {
  position: absolute;
  top: 0;
  left: 0;
  z-index: 1;
  bottom: 0;
  right: 0;
  background-color: rgba(0, 0, 0, 0.5);
  display: none;
  align-items: center;
  justify-content: center;
}
.box .cover .big-img {
  width: 380px;
}
.box .cover .close {
  position: absolute;
  top: 70px;
  left: 600px;
  background-color: red;
  color: #ffffff;
  width: 30px;
  height: 30px;
  border-radius: 5px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
}
.box .cover .close:hover {
  background-color: #960505;
}
